The present invention relates to the treatment of stress urinary incontinence "SUI," and to improved methods and surgical devices for the surgical treatment of SUI. The devices disclosed herein are additionally useful in a wide variety of other surgical procedures.
Genuine stress incontinence is the involuntary loss of urine due to a sudden rise in intra-abdominal pressure. It has been estimated that between 40% and 50% of young, healthy nulliparous women admit to occasional mild stress incontinence; however, at least 80% of stress incontinence patients are in the perimenopausal age group and are multiparous. Raz has suggested that the female urethral continence mechanism is dependent on the interaction of four urethral factors: urethral closing pressure, urethral length, urethrotrigonal anatomy, and urethral reception of intra-abdominal pressure. Raz, S., Modified bladder neck suspension for female stress incontinence, Urology, 17:82, 1981.
The urethral closing pressure is predominantly a result of the interaction of smooth and striated muscle sphincter activity, but there is also some contribution by nonmuscular urethral factors such as the submucosal vascular plexus, the elastin and collagen content of the urethral tissues, and a sphincter like effect of the mucosa. There has been considerable diversity of opinion regarding the anatomic structure and the innervation of the urethral sphincters, and a variety of views have been expressed in the literature.
Urethral length is important in the maintenance of continence. However, although it certainly interacts with other factors to contribute to continence, a short urethra alone will not produce incontinence. Urethral length varies considerably in normal women, and women with proven genuine stress urinary incontinence do not invariably have urethral shortening.
Urethrotrigonal anatomy, which can be demonstrated by lateral cystourethrography, should fulfill certain criteria. The bladder base should lie above the level of the inferior ramus of the symphysis, and with straining should not descend more than 1.5 cm. There should be a normal urethrotrigonal alignment with an angle normally less than 100 degrees, and the urethral axis should be approximately 35 degrees from the vertical. In the hypermobile situation loss of all of the normal anatomic features may occur, a radiologic finding that correlates with the clinical finding of cystourethrocele. However, clinical experience has shown that the coexistence of cystourethrocele and incontinence does not predict that the incontinence is of a genuine stress variety.
The transmission of intra-abdominal pressure to the intra-abdominal portion of the proximal urethra is also reported to be important in the maintenance of continence. This is a passive phenomenon, and is the result of the normal anatomic configuration just described. Whenever there is a rise in intra-abdominal pressure during such stresses as coughing or straining, the pressure is transmitted not only to the bladder but also to the proximal urethra, with resultant increase in the closing pressure, and prevention of leakage. If the urethral axis is altered, rotational descent will drop the proximal urethra and bladder base from its intra-abdominal location, and will obviously impair such pressure transmission.
A wide variety of operations have been used to correct this condition, generally involving the principles of elevating the bladder neck anteriorly and/or elongating and narrowing the proximal urethra. Two of the most popular operations today for stress incontinence are the Marshall-Marchetti-Krantz and Birch vesicourethropexies. The Marshall-Marchetti-Krantz technique has at least an eighty-five percent success rate, against which other operative success rates must be measured. Recently, the Pereyra operation and its modifications have enjoyed some popularity, but less than basic techniques.
Notwithstanding the foregoing, however, there remains a need for an improved treatment for SUI. Preferably, the treatment is as noninvasive as possible under the circumstances, and will eliminate or minimize hospitalization and the use of general anesthetics. In addition, there remains a need for improved medical instrumentation such as tissue cavity dilators, incision guides, bone-piercing guide drivers, and quick-connect slings and suture-securing devices for use in connection with SUI treatment and other medical procedures. U.S. Pat. No. 5,611,515, issued Mar. 18, 1997 to Benderev et al., introduces pioneering minimally invasive percutaneous and transvaginal bladder neck stabilization approaches. The percutaneous approach of Benderev et al. involves stabilizing the bladder neck using a bone anchor which is percutaneously introduced from the abdominal side of the patient. The transvaginal approach of Benderev et al. involves stabilizing the bladder neck using a staple or bone anchor which is transvaginally placed into the pubic bone. The methods and devices of the present invention may be used in several urethral or bladder neck stabilization procedures that are less invasive than many of those currently available.